Design of a new prosthetic alignment adaptor with quantitative alignment and height adjustment

Abstract

Current alignment of transtibial prostheses is based on the prosthetist's subjective opinion and on trial and error fittings. The adaptors used to align prostheses are inexact, time-consuming to operate, and do not allow height adjustment. The primary objectives of this design project were to 1) develop an alignment adaptor that allows a prosthetist to quickly and effectively align the device based on a patient's gait and stance, and 2) provide the ability to quantify the patient's specific alignment. Using computer aided design (CAD), finite element analysis (FEA), and computer aided manufacturing (CAM), a new alignment adaptor was designed and manufactured using a novel pin configuration that allows for independent height adjustment. The prototype will be tested in a prosthetist's office using two AMTI AccuSway force platforms to measure the forces, moments, and center of pressure distributions during stance and gait. Results will be used to compare three situations on each patient: no alignment, alignment with gold standard device, and alignment with new prototype. Additionally, surveys will be conducted of the prosthetist and patient to obtain qualitative feedback. The design is innovative in its quantization and height adjustment, and results of the testing are expected to show improvement over current adaptors.

Conceptual design of an alignment device for transfemoral prosthesis

“…One of them, the Staros Gardner [20] is no longer a commercial device. The commercial ones are: 4r1 of Ottobock [21], Haberman Alignment Device (HAD) [22] and Fillauer® Slide Unit [8]. On the other hand, the Polytechnic Worcester [8] and Mahidol [10] devices are currently being studied and have not yet been commercialized.…”

“…This corporation has made remarkable progress in the manufacturing and fitting of prostheses. However, in MK center as in many other centers worldwide, the static and dynamic alignment processes are mainly based on professional experience due to the lack of tools to measure the variables of the alignment process, therefore requiring more time to adapt the prosthesis to the patient [8].…”

Current overview of the state of disabled population, regarding the use of transtibial prosthesis

“…This information is used in the design of a prosthesis with an approximate functionality, degree of Liberty and forces exerted on the limb (Adebayo et al, 2011;Au et al, 2015;Bellman et al, 2008;Casallas et al, 2011;Cherelle et al, 2014;Sagawa et al, 2011;).…”

“…They use the mechanical system to simulate the effect of compensation forces necessary for the patient to maintain balance as s/he moves (Adebayo et al, 2011;Arotaritei, Turnea, Filep, Ilea and Rotariu, 2015;Casallas et al, 2011;Chen and Wang, 2015;Wang et al, 2015). The prototype is able to absorb the force generated when the prosthesis comes into contact with a surface, avoiding bounce effects, and it also compensates the angle between the basis of the prosthesis and the coupling axis, thus allowing the user to walk on steep surfaces ( Bravo and Rengifo, 2014; Morgenroth et al, 2011;Yuan et al, 2014;Zheng and Wang, 2016;Zhu, Wang, Li, Sun and She, 2015;Zhu, Wang and Wang, 2014).…”

“…In the prototype by Yuan et al(2011) a digital control system is implemented to calculate the magnitude of the force necessary for the patient to maintain balance from its own weight; the angle between the components of the prosthesis regarding the ground and the part of the prosthesis coming into contact with the floor (Adebayo et al, 2011;Bellman et al, 2008;Cherelle et al, 2014Cherelle et al, , 2012Yuan et al, 2011;Yuan et al, 2014;Zheng and Wang, 2016;Zhu et al, 2015Zhu et al, , 2014. There is only one parameter left to the patient, the other ones are calculated by sensors located in diffrent parts of the prostesis.…”